[PATCH v3 06/10] evm: Store and detect metadata inode attributes changes
Stefan Berger
stefanb at linux.ibm.com
Fri Feb 23 17:25:09 UTC 2024
On stacked filesystem the metadata inode may be different than the one
file data inode and therefore changes to it need to be detected
independently. Therefore, store the i_version, device number, and inode
number associated with the file metadata inode.
Implement a function to detect changes to the inode and if a change is
detected reset the evm_status. This function will be called by IMA when
IMA detects that the metadata inode is different from the file's inode.
Co-developed-by: Mimi Zohar <zohar at linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
---
include/linux/evm.h | 8 ++++++++
security/integrity/evm/evm.h | 6 ++++--
security/integrity/evm/evm_crypto.c | 23 ++++++++++++++++------
security/integrity/evm/evm_main.c | 30 +++++++++++++++++++++++++++--
4 files changed, 57 insertions(+), 10 deletions(-)
diff --git a/include/linux/evm.h b/include/linux/evm.h
index d48d6da32315..ddece4a6b25d 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -26,6 +26,8 @@ extern int evm_protected_xattr_if_enabled(const char *req_xattr_name);
extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
int buffer_size, char type,
bool canonical_fmt);
+extern bool evm_metadata_changed(struct inode *inode,
+ struct inode *metadata_inode);
#ifdef CONFIG_FS_POSIX_ACL
extern int posix_xattr_acl(const char *xattrname);
#else
@@ -76,5 +78,11 @@ static inline int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
return -EOPNOTSUPP;
}
+static inline bool evm_metadata_changed(struct inode *inode,
+ struct inode *metadata_inode)
+{
+ return false;
+}
+
#endif /* CONFIG_EVM */
#endif /* LINUX_EVM_H */
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index eb1a2c343bd7..b357c0ca8d23 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -39,6 +39,7 @@ struct xattr_list {
struct evm_iint_cache {
unsigned long flags;
enum integrity_status evm_status:4;
+ struct integrity_inode_attributes metadata_inode;
};
extern struct lsm_blob_sizes evm_blob_sizes;
@@ -74,11 +75,12 @@ int evm_update_evmxattr(struct dentry *dentry,
size_t req_xattr_value_len);
int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value,
- size_t req_xattr_value_len, struct evm_digest *data);
+ size_t req_xattr_value_len, struct evm_digest *data,
+ struct evm_iint_cache *iint);
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value,
size_t req_xattr_value_len, char type,
- struct evm_digest *data);
+ struct evm_digest *data, struct evm_iint_cache *iint);
int evm_init_hmac(struct inode *inode, const struct xattr *xattrs,
char *hmac_val);
int evm_init_secfs(void);
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 35416f55391c..7c06ffd633d2 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -221,7 +221,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
const char *req_xattr_name,
const char *req_xattr_value,
size_t req_xattr_value_len,
- uint8_t type, struct evm_digest *data)
+ uint8_t type, struct evm_digest *data,
+ struct evm_iint_cache *iint)
{
struct inode *inode = d_inode(d_real(dentry, D_REAL_METADATA));
struct xattr_list *xattr;
@@ -231,6 +232,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
int error;
int size, user_space_size;
bool ima_present = false;
+ u64 i_version = 0;
if (!(inode->i_opflags & IOP_XATTR) ||
inode->i_sb->s_user_ns != &init_user_ns)
@@ -294,6 +296,13 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
}
hmac_add_misc(desc, inode, type, data->digest);
+ if (inode != d_backing_inode(dentry) && iint) {
+ if (IS_I_VERSION(inode))
+ i_version = inode_query_iversion(inode);
+ integrity_inode_attrs_store(&iint->metadata_inode, i_version,
+ inode);
+ }
+
/* Portable EVM signatures must include an IMA hash */
if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
error = -EPERM;
@@ -305,18 +314,19 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value, size_t req_xattr_value_len,
- struct evm_digest *data)
+ struct evm_digest *data, struct evm_iint_cache *iint)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
- req_xattr_value_len, EVM_XATTR_HMAC, data);
+ req_xattr_value_len, EVM_XATTR_HMAC, data,
+ iint);
}
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value, size_t req_xattr_value_len,
- char type, struct evm_digest *data)
+ char type, struct evm_digest *data, struct evm_iint_cache *iint)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
- req_xattr_value_len, type, data);
+ req_xattr_value_len, type, data, iint);
}
static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
@@ -357,6 +367,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
const char *xattr_value, size_t xattr_value_len)
{
struct inode *inode = d_backing_inode(dentry);
+ struct evm_iint_cache *iint = evm_iint_inode(inode);
struct evm_digest data;
int rc = 0;
@@ -372,7 +383,7 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
data.hdr.algo = HASH_ALGO_SHA1;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
- xattr_value_len, &data);
+ xattr_value_len, &data, iint);
if (rc == 0) {
data.hdr.xattr.sha1.type = EVM_XATTR_HMAC;
rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry,
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index c658d2f1494b..c1ca0894cd8a 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -226,7 +226,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
digest.hdr.algo = HASH_ALGO_SHA1;
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
- xattr_value_len, &digest);
+ xattr_value_len, &digest, iint);
if (rc)
break;
rc = crypto_memneq(xattr_data->data, digest.digest,
@@ -247,7 +247,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
hdr = (struct signature_v2_hdr *)xattr_data;
digest.hdr.algo = hdr->hash_algo;
rc = evm_calc_hash(dentry, xattr_name, xattr_value,
- xattr_value_len, xattr_data->type, &digest);
+ xattr_value_len, xattr_data->type, &digest,
+ iint);
if (rc)
break;
rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
@@ -733,6 +734,31 @@ static void evm_reset_status(struct inode *inode)
iint->evm_status = INTEGRITY_UNKNOWN;
}
+/**
+ * evm_metadata_changed: Detect changes to the metadata
+ * @inode: a file's inode
+ * @metadata_inode: metadata inode
+ *
+ * On a stacked filesystem detect whether the metadata has changed. If this is
+ * the case reset the evm_status associated with the inode that represents the
+ * file.
+ */
+bool evm_metadata_changed(struct inode *inode, struct inode *metadata_inode)
+{
+ struct evm_iint_cache *iint = evm_iint_inode(inode);
+ bool ret = false;
+
+ if (iint) {
+ ret = (!IS_I_VERSION(metadata_inode) ||
+ integrity_inode_attrs_changed(&iint->metadata_inode,
+ metadata_inode));
+ if (ret)
+ iint->evm_status = INTEGRITY_UNKNOWN;
+ }
+
+ return ret;
+}
+
/**
* evm_revalidate_status - report whether EVM status re-validation is necessary
* @xattr_name: pointer to the affected extended attribute name
--
2.43.0
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